Well completion is performed in a wellbore to prepare the wellbore for production of hydrocarbons (from reservoirs adjacent the wellbore) or to prepare the wellbore for injection of fluids into surrounding formation. Examples of completion operations performed in a wellbore include perforating operations (in which perforating guns are lowered to a selected depth and fired to form perforations in any surrounding casing or liner and to extend perforations into surrounding formation), sand control operations (e.g., gravel packing, insertion of sand screens, and so forth), and other operations.
Various problems may occur with completion equipment installed in a wellbore to perform completion operations. The problems may result from service tool failures, bridging problems, and other causes. Bridging may occur during gravel packing, which is performed to provide sand control. Reducing sand production can be accomplished by placement of relatively large grain sand (gravel) around the exterior of a slotted, perforated, or other type pipe or sand screen. The gravel serves as a filter to reduce migration of sand with produced hydrocarbons. In a typical gravel pack completion, a sand screen is placed in the wellbore at the selected interval. Gravel is mixed with carrier fluid and pumped in slurry down a tubing and into an annulus between the sand screen and the wall of the wellbore. The carrier fluid in the slurry leaks off into the formation and/or through the sand screen. As a result, the gravel is deposited in the annulus around the sand screen where the gravel forms a gravel pack. Non-uniform gravel packing of the annulus can occur as a result of premature loss of carrier fluid from the slurry. The fluid can be lost in high permeability zones within the formation, leading to the creation of gravel bridges in the annulus before all the gravel has been placed. The gravel bridges can further restrict the flow of slurry through the annulus, which can result in voids within the gravel pack. Once production starts in the well, the flow of produced fluids will tend to be concentrated through any voids in the gravel pack, which can result in the migration of sand into the produced fluids. Also, over time, the gravel may settle and fill any void areas, which may loosen the gravel pack that is located higher up in the wellbore, potentially creating new voids.
Bridging problems and other types of problems that may occur in the wellbore are usually identified after a job (such as a gravel packing job) has been completed (post-job analysis). Even worse, a well operator may often not be aware that a problem exists until the well operator has actually started production. Once the well operator determines that a problem exists, the well may have to be shut down so that intervention can be performed to address or fix the problem(s). Intervention jobs, especially those performed at remote locations, can be expensive and can take a relatively long period of time. Also, any down time of a well can be costly.